A vehicle using fuel cells as a driving power source is generally equipped with high-pressure tanks designed to store therein a high-pressure hydrogen gas or a high-pressure hydrogen-containing gas as the fuel. One typical method of mounting the high-pressure tanks on the vehicle places the high-pressure tanks under the vehicle floor with a view to assuring sufficient spaces both for the vehicle interior and for the trunk (see, for example, JP-A 2002-370550)
This cited patent document discloses a technique of preventing a drop-out of any of the high-pressure tanks under the application of a force in a direction of moving the high-pressure tank upward. In the actual state, however, diverse forces in various directions are applied on the high-pressure tanks transversely mounted on the vehicle. A force may be applied in a direction of moving the high-pressure tank downward. In such cases, a significantly large loading may be applied onto a high-pressure piping arranged to pass through the respective high-pressure tanks.